It is a common practice to secure wear members in the form of teeth and shrouds along the digging edge of a bucket or other excavator to protect the front lip from premature wear. The teeth project forward of the lip to ease penetration and break up the ground to be gathered in the bucket. The shrouds are mounted to the lip between the teeth. As can be appreciated, the wear members, and particularly the teeth, are often placed in harsh working conditions where they are subjected to very heavy loading and a high degree of wearing.
Excavating teeth are generally composed of a multiple of parts including, for example, an adapter, a point and a lock. The adapter has a rear mounting end configured for attachment to the front lip of the bucket, and a forwardly projecting nose for mounting the point. The point is a tapered member provided with a forward earth-penetrating end and rearwardly opening socket that receives the adapter nose. The lock is fit within the wear assembly to hold the point to the adapter. Although the points wear out most frequently, the adapters are also subjected to wear and require periodic replacement.
Adapters are often welded to the bucket lip, such as in U.S. Pat. No. 4,577,423 to Hahn. Although welding securely attaches the adapter to the bucket to withstand the heavy loads, the replacement of weld-on adapters is difficult and typically performed at a shop rather than in the field. This causes the bucket to be placed out of commission, which, particularly in the case of the larger buckets, can result in a serious economic loss for the operator of a mine or other excavating site. Accordingly, the time and difficulty required to remove and install such weld-on adapters has proven to be a significant deterrent.
To enable replacement in the field, adapters have been developed that are mechanically attached to the bucket lip. The most common is known as a Whisler-style adapter (e.g., as shown in U.S. Pat. No. 4,267,653 to Hahn). In these arrangements, the rear mounting end of the adapter comprises a pair of bifurcated legs which straddle the bucket lip. Each leg of the adapter includes an opening that is aligned with a through-hole or keyway formed in the lip of the bucket. The rear ends of the legs are formed with ramp surfaces that are inclined upward and away from the respective openings. A spool and wedge are inserted into the aligned openings and through-hole to secure the adapter in place.
More specifically, the spool is generally C-shaped with arms that are configured to matingly engage the ramp surfaces of the legs. Insertion of the wedge between the spool and the front of the through-hole presses the spool rearward with the arms riding over the ramp surfaces of the legs. In this way, the arms pinch the legs against the inner and outer surfaces of the lip to secure the adapter in place. The wedge is usually inserted into the assembly by repeated blows with a large hammer. This can be an onerous and time-consuming task for field workers, especially to achieve the final movement needed to adequately hold the adapter to the lip. Further, the wedge even when tightly inserted can become loose under heavy loading, thus, risking loss of the adapter. A significant contributor to the loosening is actual stretching of the C-shaped spool under service loading, such as when the legs of the adapter shift on the lip under heavy loading. At times, the wedge is welded to the spool in its tightened position in an effort to resist such loosening. This action, however, prevents re-tightening of the lock, which allows assembly looseness, resulting in higher stresses in the wear member and a faster rate of wear on the lip. The welding together of the wedge and spool also causes removal of the lock to be more difficult.
U.S. Pat. No. 5,653,048 to Jones et al. discloses another mechanically attached adapter. In lieu of a through-hole, a boss is welded along the face of the lip. The boss is generally T-shaped and is received in a complementary slot formed in the leg of the adapter. An opening is provided at the rear end of the leg for receiving a lock. The lock, then, abuts the rear end of the boss and the rear wall of the opening to prevent the adapter from sliding forward off the boss and the lip. While this provides good support for most teeth, there is a desire for improvement for use in excavator types that deliver equally large vertical orientation loads from both the top and the bottom directions.